1. Field
The present invention generally relates to the field of infrared detectors, and more particularly to uncooled infrared detectors that are manufactured from foundry-defined silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) wafers.
2. Description of the Related Art
An uncooled (thermal) infrared detector is a device including a pixel with an infrared absorption layer (a.k.a. heat absorption layer) and a thermoelectric conversion element. The infrared absorption layer receives and converts an infrared ray (wave) into heat. The thermoelectric conversion element converts the heat into an electric signal that communicates the characteristics of the received infrared ray.
Conventional uncooled infrared detectors may have an array of pixels, each of which may include a single diode for performing the function of the thermoelectric conversion element. Generally, the single diode may have a turn-on voltage that depends on the temperature of the heat absorption layer. When the single diode conducts a constant current, the potential difference across the single diode may vary with the heat converted by the heat absorption layer. As such, the potential difference of the single diode may be used for measuring the intensity of the received infrared ray.
In order to prevent the heat from transferring among pixels, conventional uncooled infrared detectors use various types of closed well structures to thermally isolate each pixel. Typically, a closed well may be formed on the substrate layer, and it may define a cavity that surrounds the pixel. A support structure may be formed between the closed well and the pixel for suspending the pixel within the cavity. The suspended pixel, the closed well, and the support structures may be fabricated on a silicon substrate by using customer-specific fabrication processes.
However, these customer-specific fabrication processes generally involve several iterations of high precision lithography, each of which may be costly and time consuming to perform. Moreover, these customer-specific fabrication processes may suffer from low yield because the failure rates of high precision lithography are statistically high. In exchange for a better yield, some conventional infrared detectors may sacrifice the reliability of the pixels, the closed wells, and/or the support structures.
Thus, there is a need for an uncooled infrared detector with improved quality, higher yield, and lower production cost.